Water heaters are used in homes, businesses, and just about any establishment having the need to heat water. Water heaters heat water using the simple “heat rises” principle. In operation, water heaters heat water entering near the bottom of the water heater to a desired temperature using a gas-fired burner, an electric heater, or some other form of energy.
During a heating cycle, the water at the bottom of the water heater becomes hotter and begins to rise towards the top of the water heater. Denser water on top of the water being heated falls toward the bottom of the water heater, which is then heated to the desired temperature. After the temperature of the water at the bottom of the water heater reaches a certain desired temperature, the water heater stops heating the water.
When demand for hot water occurs (e.g., someone turns on a faucet to run a shower), water enters the water heater and “pushes out” or supplies the hotter water near the top of the water heater. When enough of hot water exits from the top of the water heater, cold water enters at the bottom causing the temperature of the water at the bottom of the water heater to drop below the desired temperature. The water heater then repeats the heat cycling.
A water heater typically has at least one heating element or “heater,” such as a gas-fired burner and/or electric heater. To take advantage of the “heat-rises” principle, the heater is located near the bottom of the water heater. Additionally, each water heater typically has at least one thermostat or controller for controlling the heater.
To facilitate the heating of water, the controller receives signals related to the temperature of the water. When these signals indicate that the water temperature is below a predetermined threshold, for example, when the water temperature is below 120 degrees Fahrenheit, the controller turns on the heater and the temperature of the water near the bottom of the water heater begins to rise.
After some time, the temperature of the water at the bottom of the water heater increases to a second threshold, which, for example, may be about 140 degrees Fahrenheit. When receiving signals indicating that the water temperature at the bottom of the tank is greater than the second threshold, the controller causes the heater to reduce its heat output or, alternatively, causes the heater to turn off. The heat cycle begins again when the temperature of the water at the bottom of the water heater drops below the first threshold.
Unfortunately, heating and maintaining hot water in the water heater can be expensive. To reduce operating costs, energy saving algorithms have been developed. These energy saving algorithms typically modify the inputs to the standard algorithm used by the controller to control the heat cycles of the water heater. While the user benefits from reduced operating costs, the tradeoff may be an undesirable cold shower.
Thus, it would be advantageous to have an energy savings algorithm that not only reduces the operating costs of a water heater, but also minimizes user complaints of cold water.